Devices (such as computers) and secure facilities, often contain proprietary and/or sensitive information for prolonged periods of time, wherein the information could be compromised if accessed by unauthorized individuals. Thus, such devices and facilities often employ security procedures to prevent unauthorized users from accessing, obtaining or altering such information. Such procedures (also known as access control mechanisms) employ authentication techniques to allow users to prove their identity and if authorized to do so, gain access to a given device or facility.
A number of authentication protocols have been developed to prevent unauthorized access to devices or facilities. In particular, many authentication protocols use an alphanumeric personal identification number (PIN) or password known only to the authorized user, so that when attempting to access a device or facility, the user must enter the appropriate PIN/password, to establish his/her authorization to do so. However, many users select a PIN/password that is easy to remember. Consequently, there is a significant risk that the password/PIN may be guessed or otherwise compromised, thereby enabling an attacker to gain access to the device or facility.
To minimize the risk of a password being compromised, many authentication protocols impose a limit on the number of attempts that a user may make to enter a PIN/password. This prevents an attacker from repeatedly entering different passwords until successful. In addition, many authentication protocols encourage or require users to change their PIN/password periodically.
Some authentication protocols employ one-time passwords, wherein users are assigned a secret key that may be stored on a pocket token or a computer-readable card. Under these protocols, when an attempt is made to access a device or facility, a random value (known as a challenge) is issued to the user. The pocket token or computer-readable card encrypts the challenge with the user's secret key and the user gains access to the device or facility if the encrypted challenge is correct. In order to ensure that the pocket token or computer-readable card is itself used by an authorized user, the user must also manually enter a secret alphanumeric PIN or password.
While such authentication tools reduce the risk of unauthorized access to equipment or facilities, they suffer from a number of limitations. For example, the requirement, with one-time passwords, for a user to carry a pocket token or computer-readable card may render the widespread deployment of the protocol impractical.